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Table 2 Characteristics of study cohorts

From: Enteral feeding advancement and growth until 5 years in extremely preterm infants

   Cohort 1
n = 84
Cohort 2
n = 61
Female n (%) 48 (57%) 38 (62%)e
Gestational age at birth (weeks) Median (Q1, Q3) 26.1 (24.9–27.6) 27.0 (26.0–27.7)e
Birth weight (g) Median (Q1, Q3) 740 (597–932) 785 (620–980)
Birth length (cm) Median (Q1, Q3) 33 (31–35) 33 (31–35)
Birth head circumference (cm) Median (Q1, Q3) 22.5 (22.0–25.0) 24.0 (22.5–25.7)
Infants from multiple pregnancies n (%) 22 (26.2%) 36 (59.0%)e
Twins n (%) 18 (21.4%) 28 (45.9%)
Triplets n (%) 4 (4.8%) 8 (13.1%)
Length of hospital stay (days) Median (Q1, Q3) 89 (64–109) 77 (55–102)
Postmenstrual age at discharge (weeks) Median (Q1, Q3) 39.3 (37.2–41.0) 38.4 (36.0–40.7)
Neonatal morbidities    
 Necrotizing enterocolitisb n (%) 2 (2.4%) 2 (3.3%)
 Focal intestinal perforation n (%) 5 (6.0%) 2 (3.3%)
 Intraventricular hemorrhage ≥III n (%) 7 (8.3%) 2 (3.3%)
 Periventricular leukomalacia n (%) 1 (1.2%) 3 (4.9%)
 Bronchopulmonary dysplasiaa n (%) 21 (25%) 14 (23%)
 Retinopathy of Prematurity requiring therapy n (%) 8 (9.5%) 2 (3.2%)
Total time withc
 Peripheral venous line (days) Median (Q1, Q3) 11 (7–19) 9 (5–15)e
 Central venous line (days) Median (Q1, Q3) 6 (0–14) 0 (0–6)e
 Antibiotic treatment (days) Median (Q1, Q3) 10 (5–22) 9 (5–17)
Nutrition
 Day of life when full enteral feeds were attained Median (Q1, Q3) 9 (8–11) 7 (6–9)e
Cumulative protein intake (g/kg)
 First postnatal week Median 25.5 (23.4–27.0) 24.2 (22.3–27.3)
 First postnatal 28 days (Q1, Q3) 104.6 (99.8–108.1) 109.0 (103.1–115.0)e
Cumulative parenteral protein intake (g/kg)
 First postnatal week Median (Q1, Q3) 17.9 (15.7–20.0) 10.7 (8.3–15.0)e
 First postnatal 28 days Median (Q1, Q3) 22.8 (17.1–30.3) 12.8 (8.3–22.7)e
Cumulative energy intake (kcal/kg)
 First postnatal week Median (Q1, Q3) 592 (529–625) 653 (577–721)e
 First postnatal 28 days Median (Q1, Q3) 3358 (3109–3490) 3442 (3266–3673)e
Nutrition at discharge
 Mother’s own milkd 100% n (%) 25 (30%) 32 (53%)e
 Mother’s own milkd & Formula n (%) 18 (21%) 14 (23%)
 Formula 100% n (%) 41 (49%) 15 (25%)e
Nutrition at 3 months follow up   n = 67 n = 54
 Mother’s own milkd 100% n (%) 6 (9%) 11 (20%)
 Mother’s own milkd & Formula n (%) 10 (15%) 6 (11%)
 Formula 100% n (%) 51 (76%) 37 (69%)
Duration of expressed breast milk/breastfeeding (months)   n = 39 n = 45
 Based on questionnaire Median (Q1, Q3) 5 (3–9) 5 (4–9)
  1. Cohort 1 (2006–2007): enteral feeds were initiated on day 1 with 10–15 ml/kg/day and advanced by 15–20 ml/kg/day
  2. Cohort 2 (2010): enteral feeds were initiated on day 1 with 20 ml/kg/day and advanced by 25–30 ml/kg/day
  3. a Moderate or severe BPD according to consensus definition based on oxygen supplementation or positive pressure respiratory support at 36 weeks PMA
  4. b ≥ IIa according to Bell criteria
  5. c During the entire inpatient stay
  6. d Supplemented with human milk fortifier
  7. e Significantly different between the two cohorts (p < 0.05 by Chi-square and Mann-Whitney-Test, respectively)